Not sure where best to put this, so I put it here. Feel free to move it if there's a better spot.

According to wowwiki, Blizzard currently defines ten action bars, numbered one through ten, each with twelve buttons. Bars one through six are accessible through the scrolling main action bar in either the default Blizzard interface, or nUI. Bars 7, 8, and 9 are used for different stances (warriors) or forms (druids), for the rogue stealth bar (bar 7, iirc) and possibly some other class related things. Bar 10 is currently "unassigned" and iirc does not appear in the default Blizzard interface. nUI displays bars 1 thru 6 in the scrolling main bar, but also displays bars 2-6 and 10 in the lower left and right corners of the dashboard, to right and left of the minimap, and just below the scrolling bar. So you can see 7 of the 10 bars all the time (if you have the main bar set to display bar 1) and will see bars 7,8, and 9 only when you change stances or shapeshift or whatever. I'm posting all this as background, so that folks can correct it if I'm wrong.

Now to the meat of my question: it occurs to me that it would be a good idea to assign specific things to specific bars - for example, I have mount buttons, ghost wolf (for my shaman), hearthstone, and astral recall (shaman again) on the lower right bar, whatever it's called. I tend to put food, drink, bandages and health and mana potions in the bar to the right of the minimap, and quest related buttons in the bar to the left of the minimap. I have a fairly random mix of shaman related abilities in the two bars just below the main bar. Note that I almost never use the scroll on the main bar. I find that, particularly in combat, I end up with the wrong bar "up front", so when I hit the keybinding for, say, Stormstrike, I get something else. So that's why I don't use it. On my other characters, I also tend to put class related stuff in the two bars under the main one, and mounts and stuff in the lower right one (for example), but not always in the same place as on my main (Shaman). So when I switch characters, it often takes time for me to find things, which can be bad, particularly in combat, and even more so in PvP. (I really hate what usually happens to me in PvP: "oh, here they co..." <You have died.>)

Has anyone got any ideas on how best to organize these bars and buttons, and how to organize the keybindings for the buttons?

Middle Left Bar - Other Potions, Food etc not needed immediately at hand
Middle Right Bar - Other spells and macros not immediately needed

Bottom Left Bar - Actions that I didn't need to use while in a fight such as portals for my mage and calling out pets with my warlock etc.
Bottom Right Bar - Actions that were related to my crafts. Gathering, crafting etc.

It took awhile but once I had the general layout similar switching toons wasn't as complicated.

I use the main action bar for my combat spells... all the stuff I'm constantly mashing during fights. These are my main keybind spells.

The bar below the main bar and to the right is the secondary things I use in combat... long cooldown items, items that are special case like shield wall, traps, etc. Frequently used but not constantly. These spells are also all key bound, but typically to things like alt-something or ctrl-something.

The bar to the lower left of the main bar is my off-off use spells. Things I almost never use in combat. None of them are keybound... they're one-shot items I typically just mouse-click to activate.

The bar to the left of my unit frames is my foods and pots.

The bar to the right of the unit frames is used for class specific spillover.... things I rarely use, but don't care to have to open my spell book for.

The bottom right bar, below the info panel, is used for my hearth stone, mounts and trades... cooking, first-aid, professions, fishing, etc.